Conveyance servicing structure

ABSTRACT

Conveyance servicing structure includes a truck-mounted platform and elevator structure for raising and lowering the platform to various heights for servicing conveyances of various sizes or at various levels. The platform defines a path for traffic to and from the conveyance, and the platform can extend and retract in a direction along the path. The platform can also move bodily in a direction which is lateral to the traffic path, and can also swing upwardly and downwardly. A bumper on the end of the platform can swing in a direction which is lateral relative to the path. In one embodiment, the elevator structure takes the form of a stair assembly which is extensible and includes a lower section, an upper section, and a carriage for the upper section. The stair assembly can be locked in increments of one riser height. In another embodiment, the elevator structure comprises a scissors lift.

United States Patent Smith, Sr. et a].

[ CONVEYANCE SERVICING STRUCTURE [72] lnventors: James W. Smith, Sr., Coral Gables; Beniiman E. Evans, Hialeah; William M. Riggles, Jr., Miami Lakes; Urmas Schormann, Miami, all of Fla.

[73] Assignee: Wollard Aircraft Equipment, Inc.

[22] Filed: July 20, 1970 [21] Appl. No.: 56,288

14 1 May 23, 1972 Primary Examiner-Reinaldo P. Machado Att0mey-Shanley and O'Neil [57] ABSTRACT Conveyance servicing structure includes a truck-mounted platform and elevator structure for raising and lowering the platform to various heights for servicing conveyances of various sizes or at various levels. The platform defines a path for traffic to and from the conveyance, and the platform can extend and retract in a direction along the path. The platform can also move bodily in a direction which is lateral to the traffic path, and can also swing upwardly and downwardly. A bumper on the end of the platform can swing in a direction which is lateral relative to the path. In one embodiment, the elevator structure takes the form of a stair assembly which is extensible and includesa lower section, an upper section, and a carriage for the upper section. The stair assembly can be locked in increments of one riser height. 1n another embodiment, the elevator structure comprises a scissors lift.

PATENTEBMY 2 3 I972 sum 01 or 11 INVENTORS JAMES W. SM|TH,SR. BENJIMAN E. EVANS URMAS SCHORMNN WILLIAM M. RIGGLES ATTORNEYS PATENTEDMAY 23 I972 sum on HF 11 I iflh EN v:

PATENTEDHAY 23 1972 sum 05 or 11 NF QE PATENTED m 2 3 I972 sum 07 or 11 PATENTEDHAY 23 I972 3 $64, 456

sum 08 0F 11 FIG. 18

PATENTEDMAY 23 I972 sum 10 or 11 ON 6E PATENTEDHAYZB I972 3. 664.456

sum 11 0F 11 FIG. 23

CONVEYANCE SERVICING. STRUCTURE BACKGROUND OF THE INVENTION This invention. relates to conveyance servicing structures. In

its more particular aspects, the invention pertains'to mobile;

ground crews are usually located at distances far above ground level. For loadingof passengers or cargo, or otherwise servicing aircraft, access to such elevated locations has often been obtained with the aid. of mobile. structures which. are moved to the location of the parked aircraft and into position to register with the, aircraft doorway or other. part of theiaircraft to be serviced. For example, for enplaning or deplaning passengers, mobile stairways have often been wheeled into position in registration with the aircraft doorway for. the-passengers to.enter or exit the aircraft from or to ground level.

As the vertical distances to be traversed. from. groundrto the part of the aircraft to be serviced become larger as a result of increasesinaircraft size, the equipment necessary. totraverse these distances necessarily becomes larger in order to span thelong distances involvedflhe increased sizeof the equipment made a complex operation out of what had beena relatively simple task, i.e., the accurate registration of theservicingapparatus with the part of the aircraft to be serviced. Large. servicing structures are very difficultto position accurately and rapidly, even by skilled operators. Precision is required. in manipulating the device in three dimensions (sidewise, forwardbackward, and vertically) plus orienting it in proper angular disposition relative to the aircraft. Delays for accurately positioning the servicing-equipment make for an inefficient operation and irritate passengers. Yet, the consequences of inaccurate positioning of the servicing devices can-be severe. Extensive damage to costly aircraft can result'from'ramming the aircraft'by servicing structures. Or,.a tripping:or other hazardous condition can arise from 'misalignmentof theservicingstructure relative to the aircraft, and this can result in serious injury to persons or damage to property.

Accordingly, a main object of the invention is the provision of improved conveyance servicing structures which canbe precisely positioned relative to the conveyance with rapidity, facility, and safety.

Other objectsof the inventionwill appear. from the following detailed description which, in connection .withthe accompanying schematic drawings, discloses-two embodimentsof the invention for purposesof illustration only and not for definition of the scope of the invention.

BRIEF. DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a conveyance servicing structure embodying principles of the invention.

FIG. 2 is a plan view of the structure of FIG. 1.

FIG. 3 is an enlarged view of stabilizer details of the structure of FIG. 1.

FIG. 4 is an exploded view showing the interfitting relationship of major components .of the platform of the structure of FIG. 1.

FIG. 5 is an enlarged side viewillustrating details of the platform of the structure of FIG. 1.

FIG. 6 is a cross-sectional view on line 6-6 of FIG. 5.

FIG. 7 illustrates the tilting operation of the platform.

FIG. 8 is a cross-sectional view on line 88 of FIG. 5.

FIG. 9 is a view on cross-section line 9-9 of FIG. 5.

FIG. 10 is a cross-sectional view on line 10 -10' of FIGS.

FIG. 1 l is an enlarged, side cross-sectional view showing details of the platform.

FIG. 12 is a bottom view illustrating details of the platform.

FIG. 13 is an exploded view showing the coaction of major components of the stair assembly of the structureof FIG. 1.

FIG. 14 is a side view of the stair assembly of the structure of FIG. 1. v

FIG. 15 is a cross-sectional view on line 15--15 of FIG. 14.

FIG. 16 is a view on cross-section line 16-16 of FIG. 14.

FIG. 17 is a cross-sectional view on line 17-17 of FIG. 14.

FIG. 18sis a view oncross-sectiomline 18-18 of FIG. 14.

FIG. 19 is a top view'showingdetails of the carriage of the structure .of-F IG. 1.

FIG.:20 is across-sectional view'on line 20-20 of FIG. 19.

FIG. .2l-is a viewon-cross-section line 21-21 of FIG. 19.

FIG. 22. is a. side view of another conveyance servicing structurezembodyingprinciples of the invention.

FIG. 23is an enlarged, topviewof details of the structure of FIG. 22.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS FIRST EMBODIMENT GeneralArrangement FIGS. 1 and 2depict aconveyance-servicing structure 30 in the.form.of apparatus for passengers to board or disembark 'froman aircraft-'32..The structure includesa mobile base in the formof truck 34, a stair assembly including a plurality of stair sections 36, 38 which define a'continuous stairway, and a conveyance-servicing platform'40' which defines a path for passenger traffic between the aircraft and the top of the stairway.

The stair assembly forms an elevator structure for raising and: lowering, platform:40.. Lower stair section 36 is fixedly mounted on the truck chassis, and upper stair section 38 is mounted for movementrelative to-the lower stair section to extend the stairway tothe level of the door of the aircraft to be serviced. Aircraft vary insize and their doorways vary in height:above.ground,.so the amount of extension of the upper stairsection varieswiththe particularaircraft being serviced.

Upperstair. section 38 carries conveyance servicing platform-40,.andas the. upper 'stair section is moved relative to the lower stair sectionto elongate or. shorten the stairway, the platformis thereby raised or lowered'to difierent elevations. The lplatformitself-canbe extended or retracted in a direction along; the trafiic path, can be moved bodily in a direction whichis lateralto the:traffic:path, andcan be tilted upwardly anddownwardly. A bumperonthe free end of the platform can swing in adirection which is lateral to the path of traffic.

Base

Truck 34 has the usualchassis in the form of a framework of beams includingsa beam 44at each side of:the truck. Wheels 46 mount thertruck-forrmovement across the ground, and .a

cab 48:is provided for the vehicle operator.

The :baseincludes stabilizerswhich steady the structure during loading and unloading, and control swaying in high winds. Thestabilizers include a pair of-forward or main stabilizers 50 which extend zoutboard of the truckfrom behind operator's cab 48; Apair of auxiliary or rear stabilizers 52 are provided at the rear of truck 34.

Each mainstabilizer 50is mounted onan upstanding beam 54 (FIG. 3) which is fixed to another beam 55 mounted on the truck chassis. Each stabilizer 50 includes a tubular support 56 which is pivotally mounted on beam 54 by a pin 58 carried between lugs on the beam. Another'tubular support 60 telescopically receives upper tubular' support 56. A hydraulic cylinder'assembly 62 inside the tubular supports is pivotally mounted at its upper end on tubular support 56: Operating rod 64 of hydraulic cylinder assembly 62 is pivotally mounted by pin 66 on the lower end of tubular support 60. A ground-engagingpad 68is also pivotally mounted by pin 66 on tubular support 60.

A connecting bar 70 has an outer end pivotally connected by pin 72 to tubular support 60. The inner end of connecting bar 70 is pivotally connected by pin 74 to beam 54. When operating rod 64' of hydraulic cylinder assembly 62 is retracted, tubular support 60 telescopes upwardly over tubular support 56, and the outer end of connecting bar 70 describes an are as the stabilizer swings upwardly to a stored position illustrated in phantom lines in FIG. 3. Extension of the operating rod reverses this action, swinging the stabilizer outwardly and downwardly to the operative or ground-engaging position shown in solid lines in FIG. 3. Y

Each rear stabilizer 52 includes a hydraulic cylinder assembly 76 having an upper end which is pivotally mounted by pin 78 on a beam 80 which is fixed to the truck chassis. Operating rod 82 of cylinder assembly 76 is pivotally mounted on a ground-engaging pad 84 by a pin 86, as is the lower end of a support arm 88 which has its upper end pivoted by pin 90 on beam 80. Retraction of operating rod 82 moves pad 84 upwardly to a stored position above the ground. Extension of rod 82 moves pad 84 downwardly into he ground-engaging position illustrated.

Platform Support Structure Conveyance servicing platform 40 (FIGS. 1,2) is mounted on support structure 92 at the upper end portion of upper stair section 38. Support structure 92, which is part of upper stair section 38, also forms a landing at the top of the stairway. Support structure 92 has an upper or walking surface defining a landing floor 94.

Support structure 92 is generally T-shaped in plan view (FIG. 2), having an outer segment 96 which is wider than the rest of the landing to provide a wide span of movement for platform 40 relative to support structure 92 in a direction which is lateral relative to the path of traffic over the platform. A track 98 (FIGS. 5, 12) in the form of an elongated, flat metal strip is secured to the underside of support structure 92. Track 98 extends laterally relative to the traffic path at a location spaced from the outer end portion of the wide outer segment of the support structure. A second track 100 (FIGS. 5,8) extends laterally to the path of traffic at the outer end portion of support structure 92. Track 98 is spaced from track 100 for platform-tilting action to be described.

Track 100 has a cross-sectional configuration which is curved in the shape of a circle to define a pivot for upward and downward swinging movement of platform 40 relative to support structure 92.

Platform The four major component parts or subassemblies of platform assembly 40, and their interrelationship, can be visualized from FIG. 4. Such components include a first bridge member 102 which is mounted on platform support structure 92 (FIG. A second bridge member 104 (FIG. 4) is in telescoping relationship with bridge member 102, and moves relative to bridge member 102 in the direction of arrow 106 along the path of traffic to extend or retract platform 40.

The third component subassembly of platform 40 is a flexible cover structure 108 which conceals the telescoping joint between bridge members 102, 104, to avoid a tripping hazard at the location of telescoping. The fourth component subassembly of the platform is a laterally swingable bumper member 110 which is mounted on the outer end of bridge member 104.

Bridge member 102 has a stepped configuration, with a rear or inner end portion displaced downwardly and projecting under support structure 92 (FIG. 5). The outer end portion of bridge member 102 has an upper or walking surface which is generally coplanar with walking surface 94 of support structure 92.

Bridge member 102 has a frame which includes opposite side members 112 (FIGS. 5, 12) which are joined by cross members including channels 114, 116, and 118; angle 120 (see also FIGS. 4,11); and top plate 122. Each side frame member 112 has the configuration of a box beam at the rear end portion of bridge member 102 (see FIG. 8), and has an L- shaped cross-section at the outer end portion of the bridge member (see FIGS. 9, The L-shaped portions have intumed lips 124 which define trackways for roller bearings of bridge member 104, as will be described. The outer end portion of bridge member 102 is hollow (FIG. 4), the inside walls of the frame members defining a recess for telescopically receiving bridge member 104.

At the rear end portion of bridge member 102 are two pairs of mounting lugs 126, 128 (FIGS. 5,6). The lugs project downwardly from bridge member 102, and are mounted on cross-channels 114, 116 (see also FIG. 12). A pivot pin 130 extends between lugs 126, and another pivot pin 132 is carried between lugs 128. Pin provides a pivotal mounting for a pair of lever arms 134, as does pin 132 for a pair of lever arms 136. The lever arms extend above side frame members 112 of bridge member 102, and a roller bearing is rotatably carried between the lever arms of each pair at the upper ends of the arms. Roller bearings 140 cooperate with track 98 on the underside of support structure 92. Each of a pair of parallel links 142 is mounted for pivoting movement about the roller axes at the ends of lever arms 134, 136, and the links interconnect rollers 140.

A third pair of lugs 143 (FIG. 6) projects downwardly from the frame of bridge member 102 and the lugs rotatably carry a pin 144 for pivotal mounting of a hydraulic cylinder assembly 146. Cylinder assembly 146 inclines upwardly from pin 144 and has an operating rod 148 connected to a pivot pin 150 which extends between lever arms 134.

Each of a pair of spaced-apart axles 152 (FIG. 8) is journaled in a bushing 153 (FIG. 12) which is mounted on the frame of bridge member 102 contiguous to the outer end portion of support structure 92. Each axle 152 rotatably carries a roller bearing 154 (FIG. 5,8). Roller bearings 1S4 cooperate with track 100, and in association with roller bearings 140 and track 98 serve to mount bridge member 102 for bodily rectilinear movement relative to support structure 92 in a direction which is lateral to the traffic path.

Such sidewise movement is effected by a hydraulic cylinder assembly 156 FIGS. 5, 8, 12). Cylinder assembly 156 has one end pivotally connected to a pin carried between a pair of lugs 158 which are mounted on the side frame member 1 12 which is on the right of bridge member 102 as viewed in FIG. 8. A pillow angle 160 retains the cylinder assembly in position on the left-hand side frame member 112. Operating rod 162 of cylinder assembly 156 is pivotally connected to a depending lug 164 which is mounted on the underside of support structure 92. Cylinder assembly 156 acts between support structure 92 and the frame of bridge member 102 to bodily move the bridge member relative to the support structure along tracks 100, 98 in a direction which is lateral to the path of traffic over the platform. Retraction of operating rod 162 moves the platform to the left as viewed in FIG. 8, and extension of the rod moves the platform to the right. In FIG. 2, solid lines indicate a centered position of platform 40 and phantom lines illustrate the wide limits of lateral travel of which the platform is capable. A stop 166 (FIG. 8) is positioned at each of the opposite ends of track 100, retaining rollers 154 therebetween and defining the limits of bodily lateral travel of bridge member 102.

Each roller bearing 154 has a circumferential recess or groove 168 (FIGS. 5, 8) in its tread or bearing surface. Groove 168 receives circular track 100 and is complementary in curvature to track 100 for tilting (i.e., vertically swinging) movement of bridge member 102 about track 100. This tilting action is efiected by extension and retraction of operating rod 148 (FIG. 6) of hydraulic cylinder assembly 146 at the rear end portion of bridge member 102. Cylinder assembly 146 acts upon roller bearings 140 and track 98 for swinging movement of bridge member 102 upwardly and downwardly relative to support structure 92 about track 100. Extension of operating rod 148 swings lever arms 134, 136 counterclockwise about pivot pins 130, 132 respectively to thrust rollers 140 against track 98 and thus urge the rear end portion of bridge member 102 downwardly away from support structure 92. This action swings the outer end portion of platform 40 upwardly about the line of pivoting action defined by track 100 (see FIG. 7). Retraction of operating rod 148 (FIG. 6) swings lever arms 134, 136 clockwise for movement of the rear end portion of the platform upwardly toward the underside of support structure 92 by action of gravity on the outer end portion of the platform, whereby the outer end portion of the platform swings downwardly about the track 100.

Bridge member 102 includes an angle section 172 (FIGS. 5,8) which is hooked over track 100 as a fail-safe precautionary measure to prevent the platform from falling to the ground I support structure 92 (see FIG. 7).

Bridge member 104 is telescopically received in bridge member 102 (FIG. 4, 5, 11). Bridge member 104 is moved telescopically in and out of bridge member 102 to extend and retract the platform in a direction along .the traffic path by a hydraulic cylinder assembly 176 (see also FIG. 12). Cylinder assembly 176 has oneend pivotally carried by a pin extending between a pair of lug plates 178 fixed to the underside of bridge member 102. Operating rod 180 of cylinder assembly 176 is pivoted on pin 182 which is carried by a pair of lugs 184 on a bracket on bridge member 104.

Cylinder assembly 176 acts between bridge member 102 and bridge member 104 to move bridge member-104 in and out of bridge member 102, thereby telescopically elongating .and shortening the platform in a direction along the path of traffic over the platform. Roller bearings 186 (FIG. 4, 11, 12) rotatably carried by side frame members 112 of bridge member 102 support and guide bridge member .104 as it moves in and out of bridge member 102. Guide strips .188 (FIGS. 9, 11, 12) are secured to the underside of top frame member 122 of bridge member 102. Guide strips 188 are received in ways which are defined by back-to-back, spacedapart angles 190 of the frame of bridge member 104. This guide strip and guide-way arrangement aids in maintaining correct alignment of bridge member 104 as it telescopes with bridge member 102.

Bridge member 104 has a hollow frame including side members 192 (FIGS. 9, 11) which are joined by crossmembers including rear channel 194, forward box beam 196 and angle 198. Top frame plates 200 are supported by channels 190.

Bridge member 104 rides in and out of bridge member'102 on roller bearings 186 (FIGS. 4, 11) and also upon-roller bearings 202, 204 which are rotatably mounted in polygonal plates 206 (see also FIGS. 10, 12) at the rear end portion of bridge member 104. Plates 206 are secured to frame channel 194 of bridge member 104. Roller bearings 204 ride-on inturned lips 124 (FIG. of side frame members 112 of bridge member 102. Roller bearings 202 thrust against the underside of top frame plate 122 of bridge member 102.

The upper or walking surface of bridge member 104 slides under the walking surface of bridge member 102 at the location 208 of telescoping (FIG. 11), and this necessarily produces a shoulder at this joint. The shoulder has a height which is equal to the thickness of top plate ,122 of bridge member 102 plus the clearance between the bottom surface of top plate 122 and the top surfaces of top plates 200 of bridge member 104. Cover assembly 108 (FIGS. 4, 1 1) maintains this shoulder or joint in concealed position at all times, irrespective of the position of extension of the platform.

Cover assembly 108 includes a flexible belt 210 which is drawn taut and has an upper reach or portion for covering the upper surfaces of bridge members 102, 104 at location 208 of telescoping. Mounting structure for the belt, including spacedapart rollers 212, 214, provides for elongation and shortening of the upper reach of belt 210 while maintaining tautness in the belt as bridge member 104 moves relative to bridge member 102 to extend and retract the platform. Roller 212 is rotatably mounted in a plate 213 at each side of the frame of bridge member 104, and each plate 213 is rigidly secured to the frame of bridge member 104. Roller 214 is rotatably mounted in angles 215 (FIG. 9) which are secured to side frame members 192 of bridge member 104. Rollers 212, 214 are disposed at locations spaced from one another along the traffic path (FIG. 11). Belt 210 has one end portion secured to top plate 122 of bridge member 102 under rear transition plate 174 by a plurality of screws, as 216, passing through aligned apertures in the transition plate, the belt, and top plate 122. A filler plate 218, having the same general thickness as belt 210, is provided in abutting relation with the belt under direction. The belt extends in a direction away from the free end of the platform and the belt portion of flexible cover assembly 108 then terminates at end plates 222, to which a pair of spaced-apartterminals 224 (FIGS. 4, 11) are secured. A flexible cable 226, forming part of the cover assembly, is secured to each of 'theterminals 224, and extends onwardly towards the rear end of the platform and roller 214. Cables 226 extend around and under roller 214, and extend toward the free end of platform 40. The ends of the cables are secured to eye bolts 228 which are mounted in'frame angle of bridge member 102. The effective length of the cover assembly can be adjusted by axially adjusting eye bolts 228 in angle 120. This is effected by rotation of nuts which are threaded on the eyebolts on opposite sides of the upstanding leg of angle 120.

Extension and retraction of operating rod of hydraulic cylinder assembly 176 moves bridge member 104 inwardly and outwardly relative to bridge member 102 to extend and retract the platform. Full retraction of rod 180 places the parts in the position shown in FIG. 5. FIG. 11 depicts the structure at partial extension, and FIGS. 2 and 12 depict in phantom lines the extent of elongation of which the platform is capable. As bridge member 104 moves outwardly relative to bridge member 102, flexible cover assembly 108 (FIG. 1 l) rides over rollers 212, 214 and the upper reach (i.e., the portion between the end portion secured at 216 and the forward roller 212) elongates and-the lower reach (i. e., the portion between rear roller 214 and frame angle 120) shortens an equal amount, while tautness is maintained in the cover assembly. As bridge member 104 moves inwardly, the lower reach elongates and the upper reach shortens a distance equal to the amount of elongation of the lower reach. In this way it is assured that the shoulderat'telescoping joint 208 is always covered by the upper reach of -belt'210 so that there is no tripping hazard member 234 which can make contact with an aircraft without damage to the aircraft is secured to frame channel 230. Cushion member 234 takes the form of a sheet of resilient .material (e.g. rubber) which is bent into a U-shaped configuration.

. Bumper 1 10 is mounted on bridge member 104 for swinging movement in a direction which is lateral to the traffic path. Such mounting is effected by an upstanding sleeve 236 having a vertically extending cylindrical bore which is aligned with the apertures in lugs 232, and by a pivot pin 238 which passes through sleeve 236 and through the aligned apertures in lugs 232. Bumper 110 is free to swing about the vertical axis of pin 238 in a direction either to left or to right of the traffic path. Phantom lines in FIGS. 2, 12 indicate the manner in which the bumper can swing sidewise to meet the aircraft. Forward transition plate 220 swings with the bumper, and extends sufficiently far back over the upper reach of belt 210 to prevent formation of a crevice between bumper 110 and bridge member 104 upon horizontal swinging of the bumper. Sleeve 236, transition plate 220, and mounting lugs 184 for cylinder assembly 176, all are carried by a bracket 240 which is rigidly secured to cross plate 242 which in turn is secured to box beam 196 at the forward end of the frame of bridge member 104.

Stair Assembly With reference to FIGS. 1 and 13, structure for elevating conveyance-servicing platform 40 takes the form of a stair assembly which has three major component parts or subassemblies, two of which are ramp sections in the form of stair sections 36, 38. The stair sections together define a continuous path in the form of a stairway between the ground and platform 40, for passenger traffic to and from aircraft 32.

The third major component of the stair assembly is a carriage 244 for the upper stair section. The carriage, movablymounting structure for the carriage and for the upper stair section, and a hydraulic power arrangement are provided for moving upper stair section 38 relative to lower stair section 36 in a direction along the stairway to raise and lower platform 40, at the same time elongating and shortening the stairway to the required length.

Conveyance servicing structures generally which include the stair assembly per se embody an invention which is claimed in copending application Ser. No. 55,456 filed July 16, 1970, by James F. Sauer and Leonzo V. Glidewell and entitled Conveyance Servicing Structure. However, the combination of the stair assembly with platform 40 forms a part of the present invention, particularly with respect to certain features of the platform as will be discussed hereinafter.

Lower Stair Section Lower stair section 36 comprises a frame assembly includ ing at each side a horizontal beam 246 (FIGS. 13, 14) which is rigidly secured to a side beam 44 of the truck chassis. A beam 248 inclines slightly upwardly in a direction rearwardly of the vehicle and is outboard of beam 246. Beams 246, 248 are joined by cross-beam 55, and one of the upstanding beams 54 projects from cross beam 55 at each side of the framework. A beam 254 inclines upwardly in a direction forwardly of the vehicle at each side of the lower stair frame assembly. Each beam 254 is joined to the rear end of an outboard beam 248 and to the top of an upstanding beam 54, and is fixed in position relative to the remainder of the structure of the lower stair assembly. Inclined beams 254 extend at an angle of inclination which is equal to that of the stairway.

Each of inclined beams 254 extends downwardly to a level below the respective side beam 246. Cross beams, as 258, 260, 261 are secured to the lower end portions of inclined beams 254. A side beam 262 is joined to the cross beams 258, 260

outboard of inclined beam 254 at each side of the frame, and projects rearwardly of the vehicle. An upstanding stub beam 264 at each side of the framework supports a side stringer 266 which carries the stepping assembly of the lower stair section.

The stepping assembly includes horizontal walking portions in the form of stair treads 268 and a landing 270. The landing is located at upper end portion 272 of lower stair section 36. Vertical riser portions 274 separate walking portions which are contiguous to one another in a direction along the stairway. All of the riser portions are of equal height, and all of the tread portions are of equal width.

The walking portions and the riser portions lie in planes which intersect one another at right angles to define stair nosing 276. Since all the risers are of equal height, and since all the treads are of equal width, the stair nosing defined by intersections of the planes of the treads and risers are spaced at equal distances or intervals X" in a direction along the stairway.

Each side stringer 266 carries at its upper end portion a hold-down roller bearing 278 which receives upward thrust from upper stair section 38. At each side of lower stair section 36 is a hand rail assembly 280which is supported by a plurality of balusters 282 on side stringer 266. In practice, the balusters are covered by a skin or panelling 284 which is shown in FIG. I but is removed in FIG. 14 for clarity in illustration. At lower end portion 286 (FIG. 1) of lower stair section 36 is mounted a flip-step 288 (see also FIGS. 2, l3). Flip-step 288 is pivotally mounted on side stringers 266 of stair section 36 for swinging movement about a horizontal axis defined by pivot pins joining the side stringers of the lower stair section and the sides of the flip-step. The flip-step can be rotated about from the position shown to a stored position upside down and nested between the side stringers of the lower stair section. When lowered, the flip-step affords an easy transition between the ground and the remaining steps of lower stair section 36. The lowest tread of the flip-step is preferably above ground a distance equal to the height of one of the risers of the stair section.

Carriage Carriage 244 is mounted for movement relative to lower stair section 36 by structure including inclined beams 254 (FIGS. 14, 15) of the lower stair frame assembly, and includ ing an arrangement of roller bearings on the carriage. These bearings are mounted on the carriage frame which includes at each side a generally H-shaped structure comprising an outer side frame member 290 and an inner side frame member 292 which are joined together by a web member 294. Frame members 290, 292, 294 at each side of the carriage define a downwardly opening recess for receiving an inclined beam 254 of the lower stair frame assembly. The inner side members 292 of the carriage frame are joined by a plurality of cross members 296, 298, 300 and 302 (FIGS. 19, 21). The carriage framework also includes a plurality of brace members, as 304, which strengthen the assembly.

The roller bearing arrangement includes a pair of roller bearings 306 (FIGS. l4, 15, 20) at each side of the carriage frame. The roller bearings of each pair are in opposed relation to one another, and are mounted on coaxial axles which are rotatably carried in bushings 308. One of the bushings is rigidly mounted on outer side frame member 290, and the other of the bushings is mounted on inner side frame member 292. Each of the inclined beams 254 of the lower stair frame assembly are I-section beams and have an upper flange portion 310, a lower flange portion 312, and a web portion 314. Roller bearings 306 thrust against the underside of upper flange portions 310 of the inclined beams, and the flange portions define trackways for roller bearings 306.

The roller bearing arrangement also includes a pair of roller bearings 316 (FIGS. 14, 16, 20) at each side of the carriage frame. Each roller bearing 316 is mounted on an axle rotatably carried in a bushing 318. Bushings 318 are respectively mounted in outer and inner side frame members 290, 292 with the roller bearings of each pair in opposed relation to one another. Roller bearings 316 trust against the upper side of lower flange portions 312 of inclined beams 254, which flange portions define trackways for the roller bearings. Roller bearings 306, 316 roll along the flange portions of the inclined beams, and thus cooperate with the beams for movement of the carriage relative to the beams.

Linearly extensible power means in the form of a hydraulic cylinder assembly 320 (FIGS. 13, 14, 21) are provided for moving carriage 244 relative to lower stair section 36. Cylinder assembly 320 has a lower end pivotally mounted by a pin 322 (see also FIG. 19) which is carried by a pair of lugs 324 fixed'on cross beam 260 and on a stub beam 326 of the lower stair section frame assembly. Stub beam 326 extends longitudinally of the vehicle between cross beams 258, 260. Operating rod 328 (FIGS. 19, 21) of cylinder assembly 320 has an end yoke pivotally mounted on pin 330 which is carried by lug 332 on frame cross-member 300.

Hydraulic cylinder assembly 320 acts between carriage 244 and fixed mounting lugs 324 to move the carriage on roller bearing 306, 316 along inclined beams 254. Extension of operating rod 328 moves the carriage upwardly and in a direction from left to right as viewed in FIGS. 14 and 21. Retraction of the rod moves the carriage downwardly in the opposite direction.

Upper stair section 38 comprises a frame assembly including a pair of inclined I-beams 332 (FIGS. 13, 14, 15). Beams 332 are respectively located at the opposite sides of the frame cluding inclined beams 332 and an arrangement of roller bearings on the carriage. This roller bearing arrangement includes a pair of opposed roller bearings 336 (FIGS.14, 17, 20) at each side of the carriage frame. Each roller bearing 336 is carried on an axle which is journaled in a bushing 338. One of the bushings 338 of each roller pair is mounted on an outer side frame member 290 of the carriage, and the other of the bushings is mounted on an inner side frame member 292 so that the rollers are in opposed relationship. Each beam 332 includes upper and lower flange portions 337, 339 respectively and rollers 336 engage the underside of upper flange portion 337 of the associated inclined beam 332. Rollers 336 also engage the upper side of lower flange portion 339 of the same beam. The flange portions of the beams thus define trackways for roller bearings 336.

The roller bearing arrangement of which roller bearings 336 form a part also includes a pair of roller bearings 340 (FIGS. 14, 18, 20) at each side of the carriage. Each of bearings 340 is mounted on an axle journaled in a bushing 342 and the bushings are respectively mounted in outer side frame member 290 and inner side frame member 292 so that the rollers are in opposed relation to one another. Roller bearings 340 thrust against the under side of upper flange portions 337 of beams 332, which flange portions thus define tracks for roller bearings 340.

Roller bearings 336, 340 cooperate with inclined beams 332 of upper stair section 38 for movement of the upper stair section relative to carriage 244. Centering roller bearing assemblies 344 (FIGS. l6, 18, 20) are spaced along the carriage and thrust against the web portions of the inclined beams of the upper and lower stair sections. A roller bearing 345 (FIGS. I5, 19, 20) at each side of the carriage frame runs alongthe lower flange portion of beam 332. Roller bearings 345 are adjustable vertically as viewed in FIG. to remain in contact with the lower flange portion and thereby eliminate any play which may develop in the structure.

Linearly extensible power means in the form of a hydraulic cylinder assembly 346 (FIGS. 13, 19, 21) are provided for moving upper stair section 38 relative to carriage 244.

' Cylinder assembly 346 includes a lower end which is pivotally mounted by a pin 348 (FIG. 21) carried between a pair of lugs 350 on carriage frame member 296. Operating rod 352 of cylinder assembly 346 is pivotally mounted by a pin 354 carried between a pair of lugs 356 which are fixed to a cross beam 358 in the frame of upper stair section 38 (see also FIG. 14).

Hydraulic cylinder assembly 346 acts between carriage 244 and upper stair section 38 to move upper section 38 on roller bearings 336, 340 of the carriage. Extension of operating rod 352 moves upper stair section 38 upwardly in a direction from left to right as viewed in FIGS. 14 and. 21. Retraction of operating rod 352 moves the upper stair section downwardly in the opposite direction.

Upper Stair Section The frame assembly of upper stair section 38 includes inclined beams 332 and a box beam 360 (FIG. 15) mounted on each inclined beam 332. Each box beam 360 is welded to upper flange portion 337 of an inclined beam 332, and inwardly projecting, elongated side frame plates 362 are secured to the top surfaces of beams 360. Hole-down rollers 278 (FIG. 14) of lower stair section 36 run along side frame plates 362.

Upper stair section 38 includes lower and upper end portions 364, 368 respectively (FIGS. 1,5). Platform support or landing structure 92 is located at upper end portion 368. A side stringer 370 (FIGS. 13, 15) forming part of the upper stair frame assembly is mounted on an inwardly projecting,

side frame plate 362 at each side of the: frame assembly (FIG. 15).

The upper stair section includes a plurality of horizontal walking portions in the form of stairtreads 372 and floor 94 of landing structure 92. Verticalrisers 374 separate contiguous walking portions. The walking portions and risers lie in planes which intersect at right angles todefine stair nosings 376 like stair nosings 276 of lower stair section 38. Treads 372 and risers 374 are carried by sidestringers 370.

All the risers of the upper stair section are of equal height, and all of the treads are of equal width. The height of the risers of the upper stair section is equal tothe height of the risers of the lower section, and. the width of the treads of the upper section is equal to the width of the treads of the lower section. Accordingly, stair nosings 376 defined by intersections of the planes of the treads and risers of the upper stair section are spaced at equal intervals X in .a direction along the stairway, and these intervals are equal to the intervals X" between the nosings defined by the planes of the treads and risers of the lower stair section.

Upper stair section 38 includes a hand rail 378 at each side of the stairway. Each rail is supported by a plurality of balusters 380 which are secured to beams 332 and to box beams 360. In practice, the balusters are covered by a skin or panelling 382 (FIG. 1) which is removed in FIG. 14 for clarity in illustration.

Carriage cylinder assembly 320 (FIG. 13) and upper stair section cylinder assembly 346 coact to move carriage 244 and upper stair section 38 to displace the upper stair section between a lowered position (illustrated in FIG. 14 and an extended position (illustrated in FIG. 1). In the lowered position (FIG. 14), the upper stair section underlies the lower stair section, along the lower stair section, and lower end portion 364 of upper stair section 38 is on a lower level than, and is spaced in a direction along the stairway from, upper end portion 272 of lower stair section 36.

When extended, (FIG. 1), upper stair section 38 is aligned relative to the lower stair section in an orientation in which lower end portion 364 of upper stair section 38 is contiguous to upper end portion 272 of lower stair section 36 so that the stair sections define a continuous stairway for passenger traffic to and from aircraft 32.

Locking Structure Upper stair section 38 can be raised from the position of FIG. 14 to any of a number of elevated positions short of the extended position illustrated in FIG. 1, the degree of extension of the stairway being dependent on the doorway height of the particular aircraft to be serviced. Extension is effected in increments of one step, i.e., one riser height, and there is provided a locking arrangement which, whether the stairway is fully or partly extended, locks the stair sections with a distance of one riser height between walking portions of the lower and upper stair sections. Stated differently, the locking structure locks the upper stair section relative to the lower stair section in a position in which the lowest exposed walking portion of the upper stair section (i.e., the walking portion which is closest to the landing of the lower stair section) is a distance equal to the height of one riser above the floor of the landing of the lower stair section. Which of the walking portions of the upper stair section is contiguous to the landing of the lower stair section varies with the degree of extension of the stairway.

The .upper stair section is advanced and locked in increments of one full riser height, so that all of the steps from the lower end of the lower stair section to the upper end of the upper stair section are of equal height irrespective of the amount of extension of the stairway. As will be developed, the incremental locking feature of the stair assembly has special coaction with the tilting features of the platform, which makes it possible to obtain a uniform step height all along the stairway yct-provide a servicing platform at the exact level of any aircraft door sill.

The locking structure includes a catch arrangement including a plurality of pawls, and a catch-holding arrangement in the form of a plurality of detents, and the pawls and detents cooperate to lock the stair sections in position. The pawl arrangement includes a carriage-locking pawl 384 (FIGS. 14, 16, at each side of the carriage. Pawl 384 is pivotally mounted on a bushing which is coaxial with the axle of the roller bearing 316 which is mounted in inner side frame member 292 of the carriage. Notches are formed in a rack 386 which is welded to lower flange portion 312 (FIG. 16) of each of inclined beams 254 of the lower stair section frame assembly. The detents for cooperation with carriage-locking pawls 384 take the form of a plurality of catch-retaining surfaces 388 (FIG. 20) in the notches. Detents 388 are spaced in a direction along the stairway at equal intervals X" which are equal to the intervals X between the stair nosings defined by the intersections of the planes of the treads and risers of the upper and lower stair sections.

The locking structure includes an actuating mechanism which comprises at each side of the carriage a link 390 having one end which is pivotally mounted on pawl 384 eccentrically of the axis of pivoting of the pawl. The opposite end of link 390 is pivotally connected to the lower end of another link 392 which has an upper end rigidly secured to a shaft 394 (see also FIGS. 18, 21). A return spring 396 (FIG. 20) has one end secured to an intermediate portion of link 392, and an opposite end secured to inner side frame member 292 of carriage 244.

Shaft 394 spans the carriage width (FIG. 18) and is rotatably mounted in bearings carried in bearing mounts 398 (FIGS. 19, 20) which are secured to the inner side frame members at the opposite sides of the carriage. Between bearing mounts 398, a curved arm 400 (FIGS. 18, 19, 21) has its lower end rigidly secured to shaft 394. The upper end of arm 400 is pivotally connected to a pin extending between the ears of a yoke forming a portion of a plunger 402 of a solenoid 404 which is attached to cross-member 302 of the carriage frame. Through shaft 394, solenoid 404 activates the pawl 384 at each side of the carriage.

Each carriage-locking pawl 384 is mounted on the carriage for movement between a first or locking position (illustrated in FIG. 20) in which pawl 384 operatively engages a detent 388 in rack 386 to lock the carriage against downward movement relative to the lower stair section, and a second or inoperative position in which the pawl is out of operative engagement with the detent and the carriage is free to move downwardly relative to the lower stair section. Movement of the pawl from one position to the other is effected by the actuating mechanism as follows: Energization of solenoid 404 (FIG. 21) retracts plunger 202, thereby swinging arm 400 in a counterclockwise direction, as viewed in the drawings, and thus rotating shaft 394 counterclockwise. Such rotation of shaft 394 swings each arm 392 (FIG. 20) counterclockwise against the tension of spring 396. Swinging of arm 392 moves link 390 to the right, swinging pawl 384 clockwise about the axis of bearing 316 so that the detent-engaging lower tip of the pawl swings above rack 386. As will be developed, the carriage is slightly raised (i.e., moved from left to right) relative to the lower stair section from the position illustrated before unlocking, so that the lower tip of the pawl can clear the upper edge of detent 388 and swing clockwise to unlocked position.

When solenoid 404 is deenergized, spring 396 rotates arm 392 clockwise, thereby moving link 390 to the left. This rotates pawl 384 counterclockwise, swinging its detent-engaging tip downwardly into contact with the top surfaces of rack 386. As will be more fully described, if the tip of the pawl is not at a detent, the carriage is moved downwardly along the rack (i.e., from right to left as viewed in FIG. 20) until a detent 388 is engaged by the pawl. The detents are positioned and spaced at intervals X" as noted above, so that whenever the pawl engages a detent, one of the walking portions of upper stair section 38 is at an increment of one riser height above the floor of the landing of the lower stair section. Unless, of

course, the stairway is fully lowered, when the landing floor of the upper stair section is coplanar with the floor of the landing of the lower stair section as shown in FIG. 14. FIG. 20 depicts the relative positions of the parts at one detent short of full extension of the carriage relative to the lower stair section. When the pawl engages the leftmost detent, the carriage is locked in the fully lowered position of FIG. 14.

A stop block 406 is bolted to the underside eof web 294 of the carriage frame at each side of the carriage. Each block 406 has a downwardly facing, inclined surface with is complementary with an upwardly facing, inclined surface on another stop block 408 which is bolted to the side of carriage 244. The stop blocks permit added adjustment of the locking structure, and provide a fail-safe mechanism to prevent the carriage from overriding the pawl The pawls of the locking structure also include, at each side of the carriage, an upper stair-locking pawl 410 (FIGS. 14, 18, 20). Each pawl 410 is pivotally mounted on a bushing which is coaxial with the axle of the roller bearing 340 mounted on inner side frame member 292 of the carriage. Notches are formed in an upper rack 412, one of which is welded to each of box beams 360 (FIG. 18) of the upper stair frame assembly. Detents in the form of pawl-retaining surfaces 414 (FIG. 20) in the notches are spaced along the stairway at equal intervals X which are equal to the intervals X" between the stair nosings defined by the planes of the treads and risers of the upper and lower stair sections.

The actuating mechanism for each pawl 410 includes a link 416 which has one end pivotally mounted on pawl 410 eccentrically of the axis of swing of the pawl. The opposite end of link 416 is pivotally mounted on the upper end of an am 418 which has a lower end rigidly secured to a shaft 420 (see also FIGS. 18, 19, 21). Shaft 420 is parallel to shaft 394, and is rotatably carried in bushings in bearing mounts 398.

Between the bearing mounts an arm 422 (FIGS. 18, 19) has a lower end rigidly secured to shaft 420. The upper end of arm 422 is pivotally mounted on a pin carried between the ears of a yoke (FIG. 19) of a plunder 424 of a solenoid 426 which is secured to cross-member 302 of the carriage frame. Through shaft 420, solenoid 426 actuates the pawl 410 at each side of the carriage.

Each pawl 410 is mounted on the carriage-for movement between a first or locking position (illustrated in FIG. 20) in which pawl 410 operatively engages a detent 414 of rack 412 to lock upper stair section 38 against downward movement relative to carriage 244, and a second or inoperative position in which pawl 410 is down out of operative engagement with the detent and the upper stair section is free to move downwardly relative to the carriage. Movement of pawl 410 from locking to inoperative position is effected by the actuator as follows: Energization of solenoid 426 (FIG. 19) retracts plunger 424, thereby swinging arm 422 and rotating shaft 420 (FIG. 20) counterclockwise. Rotation of shaft 420 swings arm 418 counterclockwise, thereby moving link 416 to the left and thus swinging pawl 410 clockwise about its axis so that the upper, detent-engaging tip of pawl 410 swings downwardly below the detents in rack 412. As will be described, upper stair section 38 is moved slightly upwardly (i.e., from left to right in FIG. 20) relative to the carriage from the position illustrated, to provide clearance for pawl 410 to move to inoperative position.

When solenoid 426 is deenergized, gravity acts on the lower left end portion of the pawl to swing the pawl counterclockwise so that the upper, detent-engaging tip of pawl 410 swings upwardly into contact with the bottom surfaces of rack 412. If the tip of the pawl is not at a detent, the upper stair section is moved downwardly (i.e., from right to left) and the tip of the pawl rides the bottom surfaces of rack 412 until it engages a detent 414. As with lower rack 386, the detents in the upper rack 412 are positioned, and spaced at intervals X, so that whenever pawl 410 engages a detent 414 one of the walking portions of the upper stair section is at an increment of one riser height above the landing of the lower section (unless the stairway is in the fully retracted position of FIG. 14). In FIG. 20, the parts are shown with the upper stair section fully retracted relative to the carriage. At full extension, pawls 410 engage the leftmost detent 414.

A stop block 428 is bolted to the top side of web frame member 294 at each side of the carriage. Block 428 has an inclined, upwardly facing surface which is complementary to an inclined, downwardly facing surface of another stop block 430 which is bolted to carriage 244. These stop blocks coact for rigidity in the locking structure, and aid in preventing the mass of the upper stair section from causing it to override pawls 410.

With reference to FIGS. 1, 2 and 5, a hand rail structure at the top of the stairway includes two barrier sections 432, 434 at each side of the stairway. Barrier section 432 is mounted on support structure 92 by hinge structure 436 (FIG. 5) so that barrier section 432 can swing in a direction which is lateral relative to the path of trafi'lc. Barrier section 434 has a forward end portion which is mounted on bridge member 102 for swinging movement laterally relative to the traffic path. This mounting is efiected by a downwardly projecting pivot post 438 which is rotatably received in a socket 440. Barrier sections 434, 432 are interconnected by hinge structure 442 for swinging movement relative to one another and laterally relative to the traffic path. With this arrangement, as best visualized from FIG. 2, the barrier sections swing and fold as platform 40 moves sidewise, and guard the sides of the trafiic path irrespective of the position of lateral displacement of the platform.

Socket 440 (FIG. 5) is rigidly secured to a plate 444 which is pivotally mounted by pin 446 on a side frame member 112 of bridge member 102. Pin 446 connects barrier section 434 to bridge member 102 for relative movement about a horizontal axis, so that bridge member 102 can swing relative to support structure 92 in an upward or downward direction without interference from barrier 434 (see FIG. 7).

Bridge member 102 at each side also carries a forward barrier section 448 (FIGS. 1, 5) which is pivotally mounted by pin 450 on bridge member 102 so that barrier section 448 can swing upwardly out of the way for opening an aircraft door. Barrier section 448 includes an extensible portion 452 which telescopically extends and retracts to correspond with the extension and retraction of bridge member 104.

Operation In a preferred mode of operation, conveyance servicing structure 30 (FIG. 1) is held in a storage area with stabilizers 50, 52 retracted, flip-step 288 up in nested position, and upper stair section 38 and carriage 244 in the fully retracted positions of FIG. 14. To service an aircraft, truck 34 (FIG. 1) is driven to the location of the aircraft and oriented in a position for registering the platform with the aircraft doorway. The truck is parked in this position, stabilizers 50 and 52 (FIG. 3) are lowered, and the structure is ready for extension of the stairway. Controls for these operations are housed in the cab of the truck.

The operating rod of carriage cylinder assembly 320 (FIGS. 13, 14, 21) is then extended to raise carriage 244 relative to lower stair section 36. Each of the pawls 384 (FIG. 20) can be allowed to ride the upper surfaces of rack 386 as the carriage moves to the right relative to the rack or, after the carriage has been raised slightly, solenoid 404 (FIG. 21) can be energized to move link 390 (FIG. 20) to the right to swing and hold pawls 384 up out of engagement with racks 386. In either event, upper stair section 38 remains locked to carriage 244 as the carriage moves upwardly, carrying the upper stair section.

When carriage 244 has been extended as far as desired, extension of the operating rod of carriage cylinder assembly 320 (FIG. 21) is ceased and solenoid 404, if in the energized state, is deenergized. Spring 396 (FIG. 20) rotates each pawl 384 into contact with the upper surfaces of the respective rack 386 and, if the pawl is not at a detent, the carriage is moved downwardly with the lower tip of pawl 384 riding the upper surfaces of the rack until the tip of the pawl engages a detent 388. At this time, the lowest exposed step of the upper stair section is one riser height above the floor of landing 270 (FIGS. 1, 14) of the lower stair section. The stair structure can be used in any riser-height incremental extension of the carriage relative the lower stair section for enplaning and deplaning passengers.

However, assuming that not even full extension of the carriage is sufficient to attain the height of the aircraft to be serviced, extension of the operating rod of upper stair cylinder assembly 346 (FIGS. 13, 21) is then initiated, thereby moving upper stair section 38 upwardly relative to the stationary, locked carriage. The long distance of travel of the upper stair section from the retracted position of FIG. 14 to the fully extended position of FIG. 1 is thus divided between two hydraulic cylinder assemblies 320 and 346, so that neither power means need be inordinately long. For upward movement of upper stair section 38 relative to carriage 244, each of the stair-locking pawls 410 (FIG. 20) can be allowed to ride the under surfaces of the respective rack 412 as the upper stair section 38 moves to the right relative to the'carriage. However, solenoid 426 (FIG. 19) can be actuated if desired (after the upper stair section has been slightly raised relative to the carriage) to swing and hold pawls 410 (FIG. 20) down out of engagement with racks 412.

When upper stair section 38 has been extended to bring the platform as closely as possible to coplanar relationship with the aircraft door sill, extension of the operating rod of stair cylinder assembly 346 is terminated and solenoid 426 (FIG. 19), if energized, is returned to deenergized condition. Each pawl 410 (FIG. 20) swings up into engagement with the lower surfaces of a rack 412 and if the pawl is not at a detent, the upper stair section is moved downwardly (from right to left as viewed in FIG. 20) until the tip of pawl 410 engages a detent 414. When this occurs, the lowest exposed step of the upper stair section is one riser height above the floor of landing 270 (FIGS. 1, 14) of the lower stair section and all of the steps of the stairway are of uniform height. 7

The operator then leaves the cab of the truck, moves to the rear of the vehicle, and swings flip-step 288 (FIGS 1, 13) downwardly from its stored position to the position illustrated. The operator then climbs the stairway to landing structure 92 at the top of the upper stair section where are located the controls for platform 40.

The operator manipulates the controls as needed for movement of platform 40 in three dimensions into precise registration with the aircraft doorway. Thus, if necessary the operator extends or retracts the operating rod of hydraulic cylinder assembly 156 (FIG. 12) to move platform 40 bodily sidewise to a location in exact registration with the aircraft door. The operating rod of hydraulic cylinder 176 is extended to extend the platform into close proximity with the aircraft, and the operating rod of hydraulic cylinder assembly 146 is extended or retracted as needed to tilt the platform so that the free end of the platform is precisely coplanar with the aircraft door sill. The platform is extended into contact with the aircraft and the horizontally swingable bumper 1 l0 swings to meet the aircraft fuselage thereby accommodating any non-perpendicularity of the truck (and thus of the platform) relative to aircraft 32. It will be appreciated that the tilting feature of the platform makes it possible to position the free end of the platform at the exact level of the aircraft door sill while maintaining all the walking portions of the stairway at a uniform riser height (and thus reduce tripping hazards to an absolute minimum) even though the aircraft door sill is not at an even multiple of the riser height above the ground.

With the platform positioned, if necessary, side barriers 448 (FIGS. 1, 5) are swung upwardly to allow opening of the aircraft door. The side barriers are then returned to lowered position. Extensible portions 452 are telescoped out to meet the aircraft and the structure is ready for enplaning and deplaning passengers.

When servicing of the aircraft is completed, the extensible portions of the side barriers are retracted, and platform 40 is retracted from the aircraft. Preferably, the platform is also centered within its limits of bodily sidewise and vertically swinging movement. The operator descends the stairway, swings up flip-step 288 and reenters the cab of the truck.

The operating rod of stair cylinder assembly 346 (FIG. 21) is then slightly extended to raise upper stair section 38 a very slight distance relative to the carriage, just sufficient to allow unlocking of pawls 410 (FIG. Solenoid 426 (FIG. 19) is then-energized to unlock pawls 410 (FIG. 20) and hold them downwardly out of engagement with racks 412. The operating rod of the stair cylinder assembly is then retracted, lowering upper stair section 38 downwardly along the carriage. Upon full retraction of the upper stair section relative to the carriage the solenoid is deenergized and each pawl 410 swings upwardly and catches on the highest detent 414 of the associated rack 412.

The operating rod of carriage cylinder assembly 320 (FIG. 21) is then extended very slightly, to raise the carriage a distance just sufficient to permit unlocking of pawls 384 (FIG. 20). Solenoid 404 (FIG. 21) is then energized to swing each pawl 384 (FIG. 20) upwardly and hold the pawl out of engagement with the respective rack 386. The operating rod of the carriage cylinder assembly is then retracted, lowering the carriage and the upper stair section to relative to lower stair section 36. When fully lowered, the solenoid is deenergized and each pawl 384 swings downwardly and catches on the lowest detent 388 in the associated rack 386. Stabilizers 50, 52 (FIG. 3) are then raised, and the truck is returned to its storage area.

SECOND EMBODIMENT FIGS. 22 and 23 illustrate a conveyance servicing structure 454 which forms a second embodiment of the invention. This structure takes the form of a commissary or cabin cleaning vehicle which includes a base 34', a conveyance servicing platform 40', and an elevator structure (including a scissors lift 456 and a servicing truck body 458) which raises and lowers platform 40'. Primed reference numerals denote elements which are similar to elements designated with the cor responding unprimed reference numerals in the mobile stairway embodiment of FIGS. 1-2 1.

Truck 34' has chassis beams 44' and an operators station or cab 48. An upstanding support structure 460 is fixed to chassis beams 44 directly behind cab 48', and supports platform 40 above the cab when the platform is in lowered position. The elevator structure comprises a frame assembly including a beam 462 at each side and fixed to a chassis beam 44.

Scissors lift 456 includes at each side of the structure a pair of tongs 464, 466. Tongs 464, 466 are pivotally interconnected by a pin 468. Tong 464 has a lower end portion pivotally connected by pin 470 to beam 462. The upper end portion of tong 464 is connected to a roller bearing 472 which is constrained for longitudinal movement relative to truck body 458 in a track extending along beam 474 which is secured to the underside of the truck body. The other long 466 has its upper end pivotally connected by pin 476 to beam 474. Its lower end carries a roller 478 which is constrained for movement in a track along beam 462.

A telescoping hydraulic cylinder assembly 480 has its lower end pivoted to the elevator frame assembly, and the operating rod of the cylinder assembly is pivoted by pin 482 to tong 464. Extension of the operating rod extends the tongs and retraction of the rod lowers the tongs, so that body 458 and platform 40' are moved between raised positions illustrated in solid lines in FIG. 22, and lowered positions indicated by phantom lines.

Truck body 458 has a floor or walking portion 484 which is generally coplanar with the walking surfaces of platform 40' when the platform and body are in the raised positions. The platform thus defines 'a path for trafiic between body 458 and the aircraft being serviced. A canopy 486 is slidable on rails 488 which extend longitudinally of truck body 458 and the canopy can be moved from the extended position illustrated in solid lines to a stored or retracted position illustrated in phantom lines. When extended, canopy 486 shelters platform 40' from inclement weather.

Platform 40 is mounted on truck body 458 for upward and downward bodily rectilinear movement relative to body 458 by support structure 490. Support structure 490 includes upper'and lower roller bearings 492', 494 respectively which run in tracks defined by channels 496 at the forward end portion of body 458. A stop 495 at each side of body 458 prevents the platform from dropping below the body.

Platform 40 can be extended or retracted in a direction along the traffic path by movement of bridge member 104' telescopically inwardly and outwardly relative to bridge member 102 in the same manner as platform 40 in the embodiment of FIGS. 1-21. Thus also, platform 40 can be moved bodily sidewise relative to support structure 490, and bumper accommodates non-perpendicularity of truck 34 relative to the aircraft. Platfon'n 40' is identical in all respects to platform 40, except that platform 40 does not swing vertically relative to its support structure 490. Because of the infinite positioning capability of the scissors lift, platform 40' can be positioned to be coplanar with an aircraft door sill at any elevation within the limits of vertical travel of the scissors lift. There is no need for any platform tilting feature to assure that the platform can be made coplanar with any aircraft door sill, as there is with a stairway which is locked in incremental elevations of one riser height whereby all steps are of uniform height from top to bottom of the stairway. Thus, the hydraulic cylinder assembly 146 (FIG. 6) of the mobile stairway embodiment, together with the lever arms and allied apparatus, is eliminated and platform 40' (FIG. 22) moves laterally on rollers which are fixed in position relative to bridge member 102'.

A hand rail or barrier structure is provided at each side of platform 40', and this structure includes barrier sections 498, 500 (see also FIG. 23) which are pivotally interconnected at 502. Barrier section 498 is pivotally. connected at 504 to a bar rier section 506 on platform 40'. Barrier section 500 is pivotally connected at 508 to support structure 490. Barrier sections 498, 500 swing and fold to accommodate bodily sidewise movement of platform 40' relative to support structure 490, while maintaining a safety closure at the sides of the platform.

In operation, the vehicle is held in a storage area with the parts in the positions shown in phantom lines. When needed, the vehicle is driven to the aircraft location and oriented in a general way with the aircraft doorway. The operating rod of cylinder assembly 480 is extended, and body 458 and platform 40 are raised until the platform is coplanar with the aircraft door sill. As necessary, the platform 40 is moved bodily sidewise to exact registration with the aircraft doorway, and the platform is extended into contact with the aircraft. Bumper assembly 110 swings to accommodate any non-perpendicularity or orientation of the truck relative to the aircraft.

When servicing is completed, the platform is retracted and preferably centered sidewise. The operating rod of cylinder assembly 480 is retracted to lower the body and platform. When the platform has been lowered to the level of the top of upright support structure 460, the support structure engages the platform and holds the platform over the truck cab in the position illustrated in phantom lines while body 458 continues to settle. The rollers on platform-support structure 490 move vertically along the tracks on body 458 as the body settles on the chassis. The truck is then driven to a storage area with the platform held above the cab, a highly compact arrangement.

GENERAL DISCUSSION Apparatus built in accordance with principles of the invention are highly advantageous. Precise registration of the conveyance servicing structure with the part of the conveyance to be serviced is rapidly, easily and safely accomplished, even 

1. Conveyance servicing structure, comprising a base, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform, means for extending and retracting the platform in a direction aLong the path, mounting means for mounting the platform on the elevator means for bodily movement in a direction which is lateral relative to the path, the mounting means including track means extending laterally relative to the path, and bearing means cooperating with the track means, and power means acting between the elevator means and the platform for bodily moving the platform in the direction which is lateral relative to the path.
 2. The structure of claim 1, the platform including a free end portion, bumper means, and means mounting the bumper means at the free end portion of the platform for swinging movement in a direction which is lateral relative to the path.
 3. Conveyance servicing structure, comprising a base, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform, means for extending and retracting the platform in a direction along the path, means acting between the elevator means and the platform for bodily moving the platform in a direction which is lateral relative to the path, the platform including a free end portion, bumper means, and means mounting the bumper means at the free end portion of the platform for swinging movement in a direction which is lateral relative to the path, and means for swinging the platform upwardly and downwardly relative to the elevator means.
 4. The structure of claim 3, the elevator means including a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, and means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second stair sections.
 5. Conveyance servicing structure, comprising a base, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform, means for extending and retracting the platform in a direction along the path, means acting between the elevator means and the platform for bodily moving the platform in a direction which is lateral relative to the path, and means for swinging the platform upwardly and downwardly relative to the elevator means.
 6. The structure of claim 5, the elevator means including a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, and means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second stair sections.
 7. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform, the elevator means including a support member, the platform including a first bridge member, and a second bridge member carried by the first bridge member, means for moving the second bridge member relative to the first bridge member to extEnd and retract the platform in a direction along the path, mounting means for movably mounting the first bridge member on the support member, and means acting between the support member and the first bridge member for bodily moving the first bridge member relative to the support member in a direction which is lateral relative to the path.
 8. The structure of claim 7, the platform including a free end portion, bumper means, and means mounting the bumper means at the free end portion of the platform for swinging movement in a direction which is lateral relative to the path.
 9. The structure of claim 8, including means for swinging the first bridge member upwardly and downwardly relative to the support member.
 10. The structure of claim 9, the elevator means including a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section in a direction along the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, and means for locking the stair sections with a distance substantially one riser height between contiguous walking portions of the first and second stair sections.
 11. The structure of claim 7, including means for swinging the first bridge member upwardly and downwardly relative to the support member.
 12. The structure of claim 11, the elevator means including a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section in a direction along the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, and means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second stair section.
 13. The structure of claim 7, the bridge members having upper surface and being in telescoping interrelationship, the platform including taut, flexible covering means having an upper portion for covering the upper surfaces of the bridge members at the location of telescoping, and means including roller means carried by one of the bridge members for elongating and contracting the upper portion of the flexible covering means while maintaining tautness in the flexible covering means as the second bridge member moves relative to the first bridge member to extend and retract the platform.
 14. The structure of claim 7, including a first barrier section mounted on the elevator means for swinging movement laterally relative to the path, a second barrier section mounted on the first bridge member for swinging movement laterally relative to the path, and means interconnecting the first and second barrier sections for swinging movement relative to one another and laterally relative to the path.
 15. The structure of claim 14, including means for swinging the first bridge member upwardly and downwardly relative to the support member, and means connecting the second barrier section to the first bridge member for upward and downward swinging movement of the first bridge member relative to the second barrier section.
 16. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform, the elevator means including a supPort member having an outer end portion, the platform including a first bridge member carried by the support member, and a second bridge member in telescoping relationship with the first bridge member, means for moving the second bridge member relative to the first bridge member to extend and retract the platform in a direction along the path, mounting means including cooperating bearing means and track means for movably mounting the first bridge member on the support member, the track means including first track means extending laterally relative to the path, and second track means spaced from the first track means in a direction toward the outer end portion of the support member, extending laterally relative to the path, and located contiguous to the outer end portion of the support member, the bearing means including first bearing means in cooperating relationship with the first track means, and second bearing means in cooperating relationship with the second track means, means acting between the support member and the first bridge member for bodily moving the first bridge member relative to the support member along the track means in a direction which is lateral relative to the path, and means acting upon the first bearing means and first track means for swinging the first bridge member upwardly and downwardly about the second track means, the platform including a free end portion, bumper means, and means mounting the bumper means at the free end portion of the platform for swinging movement in a direction which is lateral relative to the path.
 17. The structure of claim 16, the elevator means comprising a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section in a direction along the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, and means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second stair sections.
 18. The structure of claim 16, the first and second bridge members having upper surfaces, the platform including taut, flexible covering means having an upper portion for covering the upper surfaces of the first and second bridge members at the location of telescoping, and means including first and second spaced-apart roller means carried by the second bridge member for elongating and contracting the upper portion of the flexible covering means while maintaining tautness in the flexible covering means as the second bridge member moves relative to the first bridge member to extend and retract the platform, the flexible covering means having one end portion connected to the first bridge member and the flexible covering means extending from one end portion toward the free end portion of the platform and around the first roller means and extending in a direction away from the free end portion of the platform and around the second roller means and extending in a direction toward the free end portion of the platform to another end portion connected to the first bridge member.
 19. The structure of claim 16, the second track means having a curved cross-sectional configuration to define a pivot for upward and downward swinging movement of the first bridge member, the second bearing means including a bearing surface complementary to the curvature of the second track means.
 20. The structure of claim 19, the first bridge member having a rear end portion projecting under the support member, the support member having a walking surface portion, and the first bridge member having an outer end portion having a waLking surface portion generally coplanar with the walking surface portion of the support member.
 21. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising the lowering the platform, the elevator means including a plurality of stair sections defining a stairway, the plurality of stair sections including a first stair section and a second stair section, means for moving the second stair section relative to the first stair section to raise and lower the platform, each stair section having walking portions and riser portions, the riser portions of the stair sections being of substantially equal height, means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second stair sections, and means for swinging the platform upwardly and downwardly relative to the stairway.
 22. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a conveyance-servicing platform defining a path for traffic to and from a conveyance, elevator means carried by the base and carrying the platform for raising and lowering the platform between upper and lower limits of travel, the elevator means including means for positioning the platform at any increment of elevation within the limits of travel, means for extending and retracting the platform in a direction along the path, mounting means for mounting the platform on the elevator means for bodily movement in a direction which is lateral relative to the path, the mounting means including track means extending laterally relative to the path, and bearing means cooperating with the track means, and power means acting between the elevator means and the platform for bodily moving the platform in the direction which is lateral relative to the path.
 23. The structure of claim 22, the platform including a free end portion, bumper means, and means mounting the bumper means at the free end portion of the platform for swinging movement in a direction which is lateral relative to the path.
 24. The structure of claim 22, the elevator means including a servicing body, the platform defining a path for traffic between the servicing body and a conveyance.
 25. The structure of claim 22, the elevator means including a scissors lift.
 26. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, means defining an operator''s station carried by the base, a servicing body having a walking portion, a conveyance-servicing platform defining a path for traffic between the servicing body and a conveyance, means carried by the base and carrying the body and the platform for moving the body and the platform between lowered and raised positions, the platform and the walking portion of the body being in generally coplanar relationship when the body and platform are in raised position, and means carried by the base for supporting the platform above the operator''s station with the platform above the walking portion of the body when the body and platform are in lowered position.
 27. The structure of claim 26, including means mounting the platform on the body for upward and downward movement relative to the body. 